Graphite densification can be used to improve several properties of synthetic polycrystalline graphite. Density increase by itself is desirable in some instances. In other cases it is preferable to also enhance other physical properties such as compressive, flexural and tensile strengths. The theoretical graphite density of 2.26 has not been achieved in synthetic graphite articles. However, apparent densities of 2 and slightly higher have been obtained by densification.
A variety of such techniques are known in the art. These generally involve impregnation and high temperature isostatic pressing of a graphitized pre-form, i.e., substrate. While these processes significantly increase density, they do not achieve the greatest possible increase in structural strength. This appears to be due to a combination of graphite feed properties and process conditions.
It is therefore one object of this invention to provide an improved graphite densification process. Another object is the provision of a process for increasing the density of synthetic polycrystalline graphites while obtaining optimum increases in other structural properties such as compressive, tensile and flexural strengths. Another object is a provision of an improved graphite densification method that accomplishes the required density increase without degrading desirable properties such as crystal or pore structure and/or isotropic ratio. Another object is the provision of a method for densifying synthetic polycrystalline graphite and obtaining the most desirable physical strength and isotropic quality. Another object is the provision of a method for obtaining formed graphite articles having densities above 2 by a combination of impregnation and graphitization in a minimum number of impregnating cycles.